US Army Corps of Engineers
Rock Island District

District Projects

Big Creek Diversion Dam Sluice Gate Replacement

Published March 8, 2019

Saylorville Lake Operations Manager 
(515) 276-4656 x6504


The Saylorville Lake Project, Johnston, Iowa, also includes the Big Creek Remedial Works which consists of three dams, diversion channel, spillway and pump station. The Remedial Works protects Polk City, Iowa


The Big Creek Remedial Works Project was awarded the 1976 Chief of Engineers Distinguished Design Award. Originally Polk City was to be protected with a system of tall levees, but placing dams both above and below the city eliminated the need for those levees. The Iowa Department of Natural Resources manages the ponding area behind the Barrier Dam as an inviolate refuge during a portion of the year to protect waterfowl. The Big Creek Remedial Works provides protection for parts of Polk City Iowa and adjacent Big Creek Valley which are below the full flood pool level. This flood protection system consists of:

  1. Barrier Dam: It protects Polk City from rising water in Saylorville Lake.
  2. Pump Station: Excess water can be drained into Saylorville Lake via gravity flow through a conduit in the Barrier Dam or pumped when Saylorville Lake levels rise. There are three 24” pumps with 350 h.p. motors which are each capable of pumping 17,000 gallons per minute when Saylorville Lake level is high with 50’ of water head pressure above the pumps.
  3. Diversion Dam: It formed 880 acre Big Creek Lake and protects Polk City from floodwaters within Big Creek Watershed. A minimum 3 cfs water quality release is maintained from the Diversion Dam through Polk City into the Ponding Area.
  4. Diversion Channel & Terminal Dam/Spillway: Diverts floodwater from Big Creek Lake into Saylorville Lake. The spillway with a crest elevation of 920.0 NGVD keeps the lake level relatively stable at that elevation.


During the 1998 periodic inspection, the slanting slide gate was opened and upon closing a section of the mechanism broke 40 feet below the water surface and prevented the gate from closing. An Army National Guard bulldozer was brought in to act as a "dead man" to provide constant pressure of the stem, air intake tube and concrete supports in order to close the gate. The gate has not been opened since. A June 1999 dive report indicates the gate to be closed, but the water leakage is occurring where the structural tube/air vent enters the concrete down tube. Required release downstream into Big Creek is 3 cfs for water quality purposes.

May 2014: $9.294M contract awarded to Jensen Construction Company Des Moines Iowa to remove current slide gate structure and construct a new control tower. New control tower will feature one service gate, hoisting unit and emergency gate. This service gate will regulate a minimum outflow of 3 cfs downstream into Big Creek. Access to the control tower will be available via a service bridge from the diversion dam.


Major construction is completed.  Punch list items and closeout remain. 


OM - Operations and Maintenance 
Flood Control Act of 1958

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Additional Information

Summarized Project Costs

Estimated Federal Cost $11,500,000
Estimated Non-federal Cost $0
Estimated Total Project Cost $11,500,000
Allocations Prior to FY 2019 $0
FY 2019 Allocation $0
FY 2019 Total Capability $11,500,000


Major Work Item Current Year

FY 2019: Complete the construction of the new control tower and removal of the coffer dam.  Project construction contract closeout 3rd quarter of FY19.